Both colour and black and white photography are in widespread use for both still and moving pictures. In the television field at least, numerous techniques have been used for manipulating a television picture in various ways, e.g. by adding or inserting a second image into a window in a first image. However, the basic picture itself remains essentially unchanged.
There is also a known technique of "posterisation", which essentially reduces the image to individual areas of solid, uniform colour, rather than progressive changes in colour.
If one wants to achieve a hand drawn or painted appearance, then the principal current way of achieving this is to simply have a skilled artist draw or paint his perception of the subject in a chosen style, using conventional instruments such as pen, pencil and paintbrush.
The use of an artist is acceptable in some circumstances, and indeed it is almost certain that a human artist can always add some effect or detail that can never be achieved by a machine. Nonetheless, for many subjects, the use of an artist is either prohibitively expensive or unnecessarily time consuming. In particular, if one wishes to add such an effect to a television signal, then one has the problem of applying the effect to every frame of the signal, where there are thirty frames per second. Clearly, for even a very short sequence, the amount of work involved would be prohibitive.
Accordingly, it is desirable to provide a technique which enables a conventional colour or black and white image to be processed to achieve a variety of effects, principally giving an image a hand-drawn or painted appearance. Other more specialized effects can be provided, for example, an image can be rendered so that it appears to be a three-dimensional chrome surface. Ideally, one requires a method and apparatus that enables a variety of different techniques to be selected, manipulated and combined with one another to achieve an almost infinite variety of effects. It is further desirable that such an effect should be capable of being applied relatively quickly and economically to a digitized television or motion picture signal, or a digitized still picture or photograph.